Liquid crystal panel substrate, liquid crystal panel, and electronic equipment and projection type display device both using the same

ABSTRACT

The present invention is a liquid crystal panel substrate that comprises: pixel units each having a pixel electrode, to be used as a reflective electrode and arranged in a matrix pattern on a substrate, and a switching element controlling a voltage applied to the pixel electrode; wherein between the pixel electrode and a conductive layer forming a terminal electrode of the switching element, a contact hole is provided for connecting the pixel electrode and the terminal electrode. A light-shielding layer, having an opening surrounding the portion in which the contact hole is formed, and having no opening in regions between a plurality of adjacent pixel electrodes, is formed between the pixel electrode and the conductive layer. Harmful effects due to light leaking through a space between the pixel electrodes can thereby be prevented.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The present invention relates to liquid crystal substrates andreflective-type liquid crystal panels using the substrate, and inparticular, relates to a technique that can preferably be applied toactive-matrix liquid crystal panels in which pixel electrodes areswitched by switching elements formed on the substrate. Furthermore, thepresent invention relates to electronic equipment and projection typedisplay devices both using the liquid crystal panel.

[0003] 2. Background of Related Art

[0004] Conventionally, as active-matrix liquid crystal panels used forlight valves of projection type display devices, liquid crystal panelshaving a thin film transistor (TFT) array, employing amorphous silicon,on a glass substrate as switching elements of pixels have been put intopractical use.

[0005] Active-matrix liquid crystal panels using the above TFTs have lowTFT element mobility and a large device size. Thus, for example, aprojection type display device, such as a projector, equipped with theliquid crystal panel as a light valve, is disadvantageously large insize. Furthermore, transmissive-type liquid crystal panels have thefollowing fatal disadvantage: the aperture ratio decreases as theresolution of the panel increases, such as XGA or SXGA, since theregions of the TFTs provided for every pixel do not transmit light.

[0006] As compared with the transmissive-type active-matrix liquidcrystal panels, reflective-type active-matrix liquid crystal panels aresmall in size and have an insulated gate field effect transistor(MOSFET) array formed as switching elements on a semiconductor substrateso as to control the voltage applied to pixel electrodes which are to beused as reflective electrodes.

[0007] As is mentioned above, in active-matrix liquid crystal panelshaving transistor elements formed on a glass or semiconductor substrate,when light leaks through spaces formed between the pixel electrodes,hole-electron pairs are generated in a PN junction (e.g., a junctionbetween source/drain regions and a channel region of the transistor, ora junction between source/drain regions and a well) of the semiconductorlayer or semiconductor substrate, so that a light leakage current flowsand undesirably destabilizes the electric potential of the semiconductorlayer, the semiconductor substrate, or the well. In the case ofreflective-type liquid crystal panels, the amount of light leakage canbe reduced as compared with that of the transmissive type by, forexample, forming the pixel electrodes close to each other in the toplayer without using particular light-shielding means. However, inreflective-type liquid crystal panels used for light valves ofprojection type display devices, strong light is converged and isincident on the spaces between the pixel electrodes. Thus, it is notsufficient to arrange the pixel electrodes close to each other to avoidthe light leakage current.

[0008] In particular, since liquid crystal panels with a semiconductorsubstrate have well regions, the leaking light transmitted through notonly the transistor portion but also the portion at a certain distancefrom the transistor portion may cause a light leakage current.Therefore, unless sufficient countermeasures are taken, the lightleakage current increases as compared with liquid crystal panels havingTFTs as switching elements on a glass substrate.

[0009] Furthermore, in active-matrix liquid crystal panels havingtransistor elements on a glass or semiconductor substrate, peripheralcircuits such as a scanning side driving circuit and a data line drivingcircuit are formed on the same substrate; there is a problem such thatthe light leakage current is generated and the peripheral circuits areoperated by mistake when light enters to such peripheral circuits.

[0010] Moreover, in reflective-type liquid crystal panels, an insulatingfilm is exposed by the spaces between the pixel electrodes, and thelight reflected by the surface of the insulating film changes itsdirection by 180° and emerges. As a result, the emerging light isdisplayed as unwanted light, which deteriorates the quality of theimage.

SUMMARY OF THE INVENTION

[0011] It is therefore an object of the present invention to provide atechnique by which the amount of light leaking through the spacesbetween pixel electrodes is reduced so that the light leakage currentgenerated in a substrate decreases.

[0012] Another object of the present invention is to provide a techniquefor reducing the amount of light leaking into the pixel region andperipheral circuits without increasing the number of the process stepsin reflective-type liquid crystal panels in which pixel electrodes arearranged in a matrix pattern and peripheral circuits are providedoutside the pixel region.

[0013] Still another object of the present invention is to provide atechnique for preventing adverse effects on image quality due to thelight reflected by the surface of an insulating film exposed to thespaces between the pixel electrodes in reflective-type liquid crystalpanels.

[0014] The first through eighteenth aspects of the invention arediscussed below.

[0015] First, a liquid crystal panel substrate comprises: pixel unitseach having a pixel electrode to be used as a reflective electrode andarranged according to a matrix pattern on a substrate; and a switchingelement controlling a voltage applied to the pixel electrode;

[0016] in which between the pixel electrode and a conductive layercomprising a terminal electrode of the switching element, a contact holeis made for connecting the pixel electrode and the terminal electrode;and

[0017] a light-shielding layer, having an opening surrounding theportion in which the contact hole is formed, and having no opening inregions between a plurality of adjacent pixel electrodes, is formedbetween the pixel electrode and the conductive layer. The amount oflight leaking through the space between the pixel electrodes andreaching the switching element can thereby be reduced to substantiallyzero.

[0018] Secondly, an anti-reflection film is provided between the pixelelectrode and the light-shielding layer. The light which is incident onthe space between the pixel electrodes and reflected by the surface ofthe light-shielding layer can thereby be absorbed even when thelight-shielding layer is formed of a metallic layer having a relativelyhigh reflectance, such as aluminum.

[0019] Thirdly, the anti-reflection film has substantially the sameshape as that of the pixel electrode and is provided below the pixelelectrode. Thus, the following phenomenon can be prevented: the light,which is incident on the space between the pixel electrodes, isrepeatedly reflected between the surface of the light-shielding layerand the back surface of the pixel electrodes, leaks through an openingprovided at the portion of a connecting conductor connecting a pixelelectrode and a switching electrode, reaches a semiconductor layer or asemiconductor substrate, and generates a light leakage current.

[0020] Fourthly, the anti-reflection film is made of titanium nitride.Titanium nitride has excellent adhesion to the pixel electrode such asAl and has excellent light absorbance.

[0021] Fifthly, the film thickness of the titanium nitride is 500 to1000 angstroms. This range is preferable to absorb visible light.

[0022] Sixthly, in regions between a plurality of adjacent pixelelectrodes, a groove at least having a slope is formed on the surface ofan underlying insulating layer of the pixel electrode or on the surfaceof the light-shielding layer under the underlying insulating layer. Thelight entering through a space between the pixel electrodes can therebybe reflected in an oblique direction. Thus, the following phenomenon canbe prevented: the light incident on the space is reflected by thelight-shielding layer, emerges through the space, and is mixed with thelight reflected by the pixel electrodes. As a result, the contrast ofthe liquid crystal panel can be improved.

[0023] Seventhly, the anti-reflection film has substantially the sameshape as that of the pixel electrode and is provided below the pixelelectrode. The light reflected by the surface of the insulating film,exposed by spaces between the pixel electrodes, or the light-shieldinglayer below the insulating film, is thereby absorbed into theanti-reflection film formed on the back surface of the pixel electrodesso that the light is prevented from emerging while changing itsdirection is changed by 180°, resulting in improved image quality.

[0024] Eighthly, the anti-reflection film is made of titanium nitride.

[0025] Ninethly, the film thickness of the titanium nitride is 500 to1000 angstroms. The effects thereof are similar to those of the fourthand fifth effects.

[0026] Tenthly, the contact hole is provided at a substantially centralposition of the plane of the pixel electrode. The distance between theend portion of the pixel electrode and the opening provided in thelight-shielding layer is therefore substantially the same for each endportion. Thus, the travel distance of the light, entering through aspace between the adjacent electrodes and reaching the contact hole, isincreased and the light cannot readily reach the switching element side.

[0027] Eleventhly, a liquid crystal panel substrate comprises pixelunits which are arranged in a matrix pattern on a substrate, and each ofwhich has a pixel electrode to be used as a reflective electrode and aswitching element controlling a voltage applied to the pixel electrode;

[0028] wherein a pixel region comprising a plurality of the pixel unitsand a peripheral circuit provided at a peripheral region of the pixelregion are formed on the same substrate; and

[0029] a light-shielding layer comprising the same layer as thereflective electrode of the pixel region is formed above the peripheralcircuit. The amount of light leakage in the pixel region and theperipheral circuit can thereby be reduced, without increasing the numberof steps for producing the liquid crystal panel substrate.

[0030] Twelvethly, the light-shielding layer is positioned at aperipheral region surrounding the entire periphery of the pixel regionincluding a region in which the peripheral circuit is not formed. Thepixel electrodes are positioned around the pixel region and serve as“partitions”.

[0031] Thirteenthly, in the pixel region, a second light-shielding layeris provided between the pixel electrode and the switching element, andthe second light-shielding layer is also provided in a region betweenthe first light-shielding layer, which is provided above the peripheralcircuit, and the pixel electrodes that are outermost in the pixelregion. In the pixel region, the entrance of light from the borderbetween the pixel region and the peripheral circuit region can beprevented by providing the second light-shielding layer under the pixelelectrode.

[0032] Fourteenthly, between the pixel electrode and a conductive layercomprising a terminal electrode of the switching element, a contact holeis made for connecting the pixel electrode and the terminal electrode;

[0033] a second light-shielding layer, having an opening surrounding theportion in which the contact hole is formed in the pixel region andhaving no opening in regions between a plurality of adjacent pixelelectrodes, is formed between the pixel electrode and the conductivelayer; and

[0034] in the peripheral circuit, the second light-shielding layer isalso provided below the first light-shielding layer and is used as aconnecting line portion in the peripheral circuit. Thus, multi-layerwiring can be achieved in the peripheral circuit portion by utilizingthe light-shielding layer in the pixel region, and the driving circuitand the like can be integrated.

[0035] Fifteenthly, the second light-shielding layer has alight-shielding portion that extends or is separated from the connectingline portion. The peripheral circuit can thereby be protected from lightby double-layered light-shielding layers.

[0036] Sixteenthly, the present invention can provide a liquid crystalpanel which suppresses a reduction in contrast due to the light leakagecurrent, and which comprises: a liquid crystal panel substrate accordingto the above-mentioned present invention; a light-incident-sidesubstrate positioned opposing the liquid crystal panel substrate with aspace therebetween; and a liquid crystal filled in the space.

[0037] Seventeenthly, the present invention can provide electronicequipment which is equipped with the above liquid crystal panel as adisplay portion, and which have a reflective type display device havingexcellent contrast at low electric power consumption.

[0038] Eighteenthly, the present invention can provide a small-sizedprojection type display device which has excellent contrast, and whichcomprises: a light source; the above liquid crystal panel reflecting andmodulating the light emerging from the light source; and a projectionoptical means for collecting and projecting the light modulated by theliquid crystal panel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]FIG. 1(a) is a cross-sectional diagram showing an embodiment of apixel region on a reflective-electrode-side substrate of areflective-type liquid crystal panel to which the present invention isapplied. FIG. 1(b) is a cross-sectional diagram showing a border betweena pixel region and a peripheral region in the reflective-electrode-sidesubstrate of the reflective-type liquid crystal panel incorporated inthe present invention.

[0040]FIG. 2 is a cross-sectional diagram showing a peripheral region ina reflective-electrode-side substrate of a reflective-type liquidcrystal panel incorporated in the present invention.

[0041]FIG. 3 is a plan layout diagram showing the embodiment of a pixelregion in the reflective-electrode-side substrate of the reflective-typeliquid crystal panel incorporated in the present invention.

[0042] FIGS. 4(a), 4(b) and 4(c) are cross-sectional diagrams showingother embodiments of a structure of a space between pixel electrodes ina reflective-electrode-side substrate of a reflective-type liquidcrystal panel incorporated in the present invention.

[0043]FIG. 5 is a plan diagram showing a structural example of a circuitlayout of a reflective-electrode-side substrate of a reflective-typeliquid crystal panel of the embodiment.

[0044]FIG. 6 is a cross-sectional diagram showing a structural exampleof a reflective-type liquid crystal panel to which the liquid crystalpanel substrate of the embodiment is applied.

[0045]FIG. 7 shows wave-forms of the voltages applied to the gate lineand the data line of a switching element of a pixel in a reflective-typeliquid crystal panel incorporated in the present invention.

[0046]FIG. 8 is a diagram showing a projection type display device towhich the reflective-type liquid crystal panel of the embodiment isapplied as a light valve.

[0047] FIGS. 9(a), 9(b) and 9(c) each show electronic equipment usingthe reflective-type liquid crystal panel of the present invention.

[0048]FIG. 10 is a cross-sectional diagram showing another embodiment ofa reflective-electrode-side substrate incorporated in the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0049] Preferred embodiments of the present invention will be explainedwith reference to accompanying drawings.

[0050] (Description of a Liquid Crystal Panel Substrate Using aSemiconductor Substrate)

[0051] FIGS. 1(a), 1(b) show the first embodiment of areflective-electrode-side substrate of a reflective-type liquid crystalpanel incorporated in the present invention. Among pixels arranged in amatrix pattern, one pixel is shown by the cross-sectional diagram andthe plan layout in FIGS. 1(a), 1(b), respectively. FIG. 1(a) is across-sectional diagram taken along the line I-I in FIG. 3. Similarly,FIG. 1(b) is a cross-sectional diagram taken along the line II-II inFIG. 3.

[0052] In FIGS. 1(a), 1(b), reference numeral 1 indicates a P-typesemiconductor substrate (may be an N-type semiconductor substrate (N⁻))such as single-crystal silicon, numeral 2 indicates a P-type well regionformed on the surface of the semiconductor substrate 1, and referencenumeral 3 indicates a field oxide film (so-called LOCOS) for separatingelements, which is formed on the front surface of the semiconductorsubstrate 1. Although the well region 2 is not particularly limited, itis formed as a common well region of a pixel region formed by arrangingpixels in a matrix pattern, such as 768×1024. Furthermore, the wellregion 2 may be formed separately from the well regions in whichtransistor elements comprising peripheral circuits are formed, such as adata-line driving circuit 21, a gate-line driving circuit 22, an inputcircuit 23, and a timing control circuit 24, as is shown in FIG. 5illustrating a plan diagram of the whole liquid crystal panel substrate.

[0053] The carriers generated in a well region, in which the peripheralcircuit elements operated by high-frequency clock are formed, flow intoanother well region of the pixel region, thereby causing the pixeltransistors to malfunction. The malfunction can be prevented byseparating the wells. In addition, the following effect of electrostaticnoise from outside can also be prevented by separating the wells: noiseenters the well region from the input circuit 23, reaches the portion ofthe well in the pixel region, and causes pixel transistors tomalfunction.

[0054] The field oxide film 3, with a thickness of approximately 5000 to7000 angstroms is formed by selective heat oxidation. In the field oxidefilm 3, each pixel has two openings such that a gate electrode 4 a, madeof poly-silicon, metallic silicide, etc. is formed in the center of oneopening with a gate oxide film (insulating film) 4 b interposedtherebetween, and source and drain regions 5 a and 5 b both formed of alayer doped with a high concentration of N-type impurity (hereinafterreferred to as doping layer) are formed at both sides of the gateelectrode 4 a on the surface of the substrate to form a field effecttype transistor (MOSFET) as a switching element. The gate electrode 4 ais extended in the scanning line direction (pixel row direction) to forma gate line 4.

[0055] A P-type doping region 8 is formed on the surface of thesubstrate in the other opening made in the field oxide film 3, and agate electrode 9 a, made of poly-silicon, metallic silicide, etc. isformed on the surface of the P-type doping region 8 with a gate oxidefilm (insulating film) 9 b interposed therebetween so as to form aninsulating film capacitor between the electrode 9 a and the P-typedoping region 8. The electrode 9 a can be formed by the same process asthat of the poly-silicon or metallic silicide layer to be used as thegate electrode 4 a of the MOSFET, and the insulating film 9 b below theelectrode 9 a can be formed by the same step as that of the insulatingfilm to be used as the gate insulating film 4 b.

[0056] The insulating films 4 b and 9 b, with thicknesses ofapproximately 400 to 800 angstroms, are formed on the surface of thesemiconductor substrate inside the openings by heat oxidation. Theelectrodes 4 a and 9 a are formed such that an approximately 1000 to3000 angstroms thick silicide layer is formed from a refractory metal,such as Mo or W, on an approximately 1000 to 2000 angstroms thickpolysilicon layer. The source and drain regions 5 a and 5 b are formedin a self aligned manner as follows: by ion implantation, N-typeimpurities are doped into the surface of the substrate at both sides ofthe gate electrode 4 a using the gate electrode 4 a as a mask. A portionof the well region just below the gate electrode 4 a is used as achannel region 5 c of the MOSFET.

[0057] In addition, preferably, the P-type doping region 8 is formed bydoping using exclusive ion implantation and heat treatment, and isformed by ion implantation before forming the gate electrode. In otherwords, after forming the insulating films 4 b and 9 b, impurities havingthe same polarity as that of the well are implanted such that thesurface of the well has a higher impurity concentration than the well soas to achieve low resistance. The preferred impurity concentration ofthe well region 2 is not more than 1×10¹⁷/cm³, and more preferably,1×10¹⁶ to 5×10¹⁶/cm³. Although the preferred surface impurityconcentration of the source and drain regions 5 a and 5 b is 1×10²⁰ to3×10²⁰/cm³ and the preferred surface impurity concentration of theP-type doping region 8 is 1×10¹⁸ to 5×10¹⁹/cm³, 1×10¹⁸ to 1×10¹⁹/cm³ isparticularly preferable from the perspective of reliability and pressuredurability of the insulating film forming a holding capacitor.

[0058] A first interlayer insulating film 6 informed on the electrodes 4a and 9 a and the field oxide film 3; data lines 7 (see FIG. 3), sourceelectrodes 7 a extended from the data lines, and auxiliary connectinglines 10 are formed of a metallic layer essentially consisting ofaluminum and provided on the insulating film 6 such that each sourceelectrode 7 a is electrically connected to the source region 5 a via acontact hole 6 a made in the insulating film 6, one end of eachauxiliary connecting line 10 is electrically connected to the drainregion 5 b via a contact hole 6 b made in the insulating film 6, and theother end of each auxiliary connecting line 10 is electrically connectedto the electrode 9 a via a contact hole 6 c made in the insulating film6.

[0059] For example, the insulating film 6 is formed by depositing athickness of approximately 8000 to 10000 angstroms of BPSG film (asilicate glass film containing boron and phosphorus) on HTO film (asilicon oxide film formed by high-temperature CVD) having a thickness ofan approximately 1000 angstroms. For example, the metallic layer formingthe source electrode 7 a (data line 7) and the auxiliary connecting line10 has a four-layer structure of Ti/TiN/Al/TiN from the bottom layer.The thickness of each layer is as follows: 100 to 600 angstroms for thelower Ti layer, approximately 1000 angstroms for the TiN layer, 4000 to10000 angstroms for the Al layer, and 300 to 600 angstroms for the upperTiN layer.

[0060] A second interlayer insulating film 11 is formed over the sourceelectrode 7 a, the auxiliary connecting line 10, and the interlayerinsulating film 6, and a light-shielding layer (light-shielding layer),formed of a second metallic layer 12 essentially comprising aluminum, isformed on the second interlayer insulating film 11. The second metalliclayer 12 forming the light-shielding layer is also used as a metalliclayer forming a connecting line between elements in the peripheralcircuits such as a driving circuit formed around the pixel region, as isdiscussed below.

[0061] Therefore, it is unnecessary to add an extra step for forming thelight-shielding layer 12, resulting in a simpler process. Thelight-shielding layer 12 covers the entire pixel region, except for anopening 12 a, made at a position corresponding to the auxiliaryconnecting line 10, so as to pass a columnar connecting plug 15electrically connecting the undermentioned pixel electrode to theMOSFET. In other words, in the plan view shown in FIG. 3, a rectangularframe indicated by the reference numeral 12 a indicates the opening, andthe outside of the opening 12 a is the light-shielding layer 12. Lightincident on the upper side of FIG. 1 (the liquid crystal layer side) canthereby be cut off almost completely. Thus, it is possible to preventthe light leakage current generated by the light incident on the channelof the MOSFET used for switching the pixel and well regions.

[0062] For example, the second interlayer insulating film 11 is formedas follows: using TEOS (tetraethylorthosilicate) as a material, asilicon oxide film (hereinafter referred to as TEOS film) of a thicknessof approximately 3000 to 6000 angstroms is deposited by plasma CVO; anSOG film (spin on glass film) is deposited thereon and trimmed by etchback; and a second TEOS film of a thickness of approximately 2000 to5000 angstroms is deposited thereon. The second metallic layer formingthe light-shielding layer may be the same as that of the first metalliclayer 7 (7 a), and for example, it can have the four-layer structure ofTi/TiN/Al/TiN from the bottom layer. The thickness of each layer is asfollows: 100 to 600 angstroms for the bottom Ti layer, approximately1000 angstroms for the TiN layer, 4000 to 10000 angstroms for the Allayer, and 300 to 600 angstroms for the top TiN layer.

[0063] According to this embodiment, a third interlayer insulating film13 is formed on the light-shielding layer 12, and on the thirdinterlayer insulating film 13, a pixel electrode 14 is formed as arectangular reflective electrode substantially corresponding to onepixel, as is shown in FIG. 3. A contact hole 16 penetrating the thirdinterlayer insulating film 13 and the second interlayer insulating film12 is formed inside the opening 12 a made in the light-shielding layer12, and the columnar connecting plug 15, which is made of a refractorymetal such as tungsten, and which electrically connects the auxiliaryconnecting line 10 to the pixel electrode 14, is placed in the contacthole 16. In addition, a passivation film 17 is formed on the entirepixel electrode 14.

[0064] For assembling a liquid crystal panel, an alignment film isfurther formed on the reflective-electrode-side substrate, and then, anopposing substrate is positioned facing the substrate with apredetermined space therebetween. An opposing electrode (commonelectrode) is formed on the inner side of the opposing substratebeforehand, and the alignment film is formed thereon. The periphery ofthe pair of substrates is fixed by a sealing member, and then, a liquidcrystal is poured and encapsulated into the thus-formed space to form aliquid crystal panel.

[0065] Although it is not particularly limited, after depositingtungsten, etc. comprising the connecting plug 15 by CVD, the tungstenand the third interlayer insulating film 13 are planarized by a CMP(chemical machine polish) method, the pixel electrode 14 is prepared,for example, by forming an aluminum layer of a thickness ofapproximately 300 to 5000 angstroms according to a low-temperaturesputtering method, and formed into a square-like shape whose sides areapproximately 15 to 20 μm by patterning. The connecting plug 15 may beformed by making a contact hole after planarizing the third interlayerinsulating film 13 by the CMP method, and then, depositing tungsteninside the contact hole. As the passivation film 17, a silicon oxidefilm of a thickness of approximately 500 to 2000 angstroms is used forthe pixel region, and a nitrogen oxide film of a thickness ofapproximately 2000 to 10000 angstroms is used for the peripheral circuitportion, sealing portion 36, and a scribe portion of the substrate. Thesealing portion is formed by a sealing member for fixing a pair ofsubstrates to assemble a liquid crystal panel, as is mentioned above.The scribe portion is a portion along the scribe region (i.e., the endportion of the liquid crystal panel substrate) for separating numerousreflective-side liquid crystal panel substrates of the presentinvention, formed in a semiconductor wafer, into semiconductor chipsalong scribe lines by dicing.

[0066] In addition, by using a silicon oxide film as the passivationfilm 17 covering the pixel region, it is possible to prevent thereflectance from changing a great amount due to a variation in the filmthickness or in response to a wavelength of the light.

[0067] J Meanwhile, a silicon nitride film, which is superior to thesilicon oxide films as a protective film in the light of waterresistance of the substrate, etc. is employed as the passivation film 17covering the peripheral region of the substrate, particularly, outsidethe region in which the liquid crystal is encapsuled (outside thesealing member). The reliability can further be increased by employing amono-layer structure having a silicon nitride film or a double-layerstructure having a silicon nitride film formed on a silicon oxide film.In other words, moisture, etc. readily enters the peripheral region ofthe substrate exposed to the atmosphere, particularly in the scribeportion. Thus, the reliability and durability can be improved bycovering such a portion with a protective film of silicon nitride.

[0068] Wavelength dependency of the reflectance of the pixel electrodecan be reduced in a reflective-side liquid crystal panel by setting thethickness of the passivation film formed on the reflective electrode towithin a range of from 500 to 2000 angstroms. At the time of assemblingthe liquid crystal panel, an alignment film made of a polyimide isformed on the entire surface of the passivation film 17 and subjected torubbing.

[0069]FIG. 3 is a plan layout diagram illustrating the reflective-sideliquid crystal panel substrate shown in FIG. 1. As is shown in thefigure, the data line 7 and the gate line 4 are formed to cross eachother in this embodiment. Since the gate line 4 also serves as the gateelectrode 4 a, the portion of the gate line 4 indicated by hatching H inFIG. 3 is used as the gate electrode 4 a, and a channel region 5 c ofthe pixel switching MOSFET is formed on the surface of the substratebelow the gate electrode 4 a. Source and drain regions 5 a and 5 b areformed on the surface of the substrate at both sides of the channelregion 5 c (shown as the upper and lower sides in FIG. 3). The sourceelectrode 7 a connected to the data line is formed such that it extendsfrom the data line 7 provided along the vertical direction of FIG. 3 andis connected to the source region 5 a of the MOSFET via a contact hole.

[0070] In addition, the P-type doping region 8 forming one terminal ofthe holding capacitor is formed in parallel to the gate line 4 (pixelrow direction) and connected to a P-type doping region of the adjacentpixel. The P-type doping region 8 is connected to a power source line 70via a contact hole 71, and a predetermined voltage V_(ss), such as 0 V(ground voltage), is applied to the P-type doping region 8. Thepredetermined voltage V_(ss) may be the same as, or approximately equalto, the voltage of the common electrode provided on the opposingsubstrate, the same, or approximately equal to, the center voltage ofthe amplitude of image signals supplied to the data line, or theintermediate voltage between the common electrode voltage and the centervoltage of the amplitude of image signal voltage.

[0071] By commonly connecting each P-type doping region 8 to the voltageV_(ss) in the outside of the pixel region, the voltage of one electrodeof the holding capacitor is stabilized and the holding voltage held bythe holding capacitor during the non-selected period of the pixel(non-conducting period of the MOSFET) is stabilized. Thus, variation involtage applied to each pixel electrode during one frame period can bereduced. In addition, undesired voltage variation of the pixel electrodecan be prevented. Furthermore, since the P-type doping region 8 ispositioned near the MOSFET and the voltage of the P well issimultaneously fixed, the fundamental voltage of the MOSFET isstabilized. Thus, the variation in the threshold voltage due to the backgate effect can be prevented.

[0072] Although not shown in the figures, the power source line 70 isalso used for supplying the predetermined voltage V_(ss), as the wellvoltage, to the P-type well region of the peripheral circuits providedoutside the pixel region. The power source line 70 is formed of a firstmetallic layer which is the same as the data line 7. The pixel electrode14 is formed in a rectangular shape, provided near an adjacent pixelelectrode 14 at a distance of, for example, 1 μm, so as to reduce asmuch as possible the amount of light leaking through the spaces betweenthe pixel electrodes.

[0073] In the figures, the center of the shape of the pixel electrode isshifted from that of the contact hole 16. However, it is preferred thatthese centers are substantially coincident with, or superimposed onto,each other to reduce the amount of light leakage, since the traveldistance of the light, incident on the space between pixel electrodes,from the end portion of the pixel electrode to the contact hole, therebybecomes substantially the same for each end portion. This is because,since the second metallic layer 12 having light-shielding light isopened by the opening 12 a in the periphery of the contact hole 16, ifthe opening 12 a is provided near the end portion of the pixel electrode14, light which is incident from the space between the pixel electrodesis irregularly reflected between the second metallic layer 12 and theback surface of the pixel electrode 14, reaches the opening 12 a, and isincident to the lower substrate side from the opening, resulting inlight leakage. Therefore, by substantially matching or superimposing thecenter of the pixel electrode with that of the contact hole 16, thetravel distance of the light, incident on the space between the pixelelectrodes, from the end portion of the pixel electrode to the contacthole, thereby becomes substantially the same for each end portion of thepixel electrode. Thus, preferably, the light cannot readily reach thecontact hole, through which the light may enter the substrate side.

[0074] In the above embodiment, a case in which the pixel switchingMOSFET is an N-channel type, and the semiconductor region 8 to be usedas one electrode of the holding capacitor is a P-type doping layer isdescribed. However, it is also possible to have an N-type as the wellregion 2, a P-channel type as the pixel switching MOSFET and an N-typedoping layer as the semiconductor region to be used as one electrode ofthe holding capacitor. In such a case, similarly to the N-type wellregion, it is preferred that a predetermined voltage V_(DD) is appliedto the N-type doping layer to be used as one electrode of the holdingcapacitor. The predetermined constant voltage VDD is preferably thevoltage of the higher side of the power source voltage, since it isapplied to the N-type well region. In other words, when the image signalvoltage applied to the source/drain of the pixel switching MOSFET is 5V, the predetermined constant voltage V_(DD) is preferably set to 5 V.

[0075] In addition, since a logic circuit and the like such as a shiftregister of the peripheral circuits are driven by a small voltage suchas 5 V (some of the peripheral circuits such as a circuit supplyingscanning signals to the gate lines are driven at 15 V), while a largevoltage such as 15 V is applied to the gate electrode 4 a of the pixelswitching MOSFET, the following technology is considered: the gateinsulating film of a FET forming a peripheral circuit driven at 5 V isformed to be thinner than the gate insulating film of a pixel switchingFET (by forming the gate insulating film by a separate step or byetching the surface of the gate insulating film of the FET of aperipheral circuit) so as to increase the operation speed of theperipheral circuit (particularly the shift register of thedata-line-side driving circuit, for which high-speed scanning isrequired) by improving the response characteristics of the FET of theperipheral circuit. By employing this technique, the thickness of thegate insulating film of the FET forming a peripheral circuit can bedecreased to approximately one third to one fifth (e.g. 80 to 200angstroms) of that of the gate insulating film of the pixel switchingFET in light of the pressure durability of the gate insulating film.

[0076]FIG. 7 shows the driving waveforms in the first embodiment. In thefigure, V_(G) indicates the scanning signal applied to the gateelectrode of the pixel switching MOSFET, period t_(1H) indicates theselected period (scanning period) during which the MOSFET of the pixelconducts, and the other period is the non-selected period during whichthe MOSFET of the pixel does not conduct. Furthermore, V_(d) indicatesthe maximum amplitude of the image signals applied to the data line,V_(c) indicates the center voltage of the image signals, and LCCOMindicates the common voltage applied to the opposing (common) electrodeformed on the opposing substrate facing the reflective-electrode-sidesubstrate.

[0077] The voltage applied between the electrodes of the holdingcapacitor is determined by the difference between the image signalvoltage V_(d) applied to the data line shown in FIG. 8 and thepredetermined voltage V_(ss) such as 0V applied to the P-typesemiconductor region 8. However, the necessary voltage differencefundamentally required to be applied to the holding capacitor isapproximately 5V, which is the difference between the image signalvoltage V_(d) and the center voltage V_(c) of the image signals(although the common voltage LC-COM applied to the opposing (common)electrode 33 provided on the opposing substrate 35 of the liquid crystalpanel shown in FIG. 6 is shifted by ΔV from the V_(c), the actualvoltage applied to the pixel electrode is shifted by ΔV and becomesV_(d)-ΔV). Thus, in the first embodiment, it is possible that the dopingregion 8 forming one terminal of the holding capacitor has a polarityopposite to that of the well (arranged to be N-type in the case of aP-type well), and is connected to the voltage of approximately V, orLC-COM in the periphery of the pixel region so as to have a differentvoltage from the well voltage (e.g., the P-type well is at V_(ss)). Theinsulating film 9 b, just below the poly-silicon or metallic silicidelayer forming one electrode 9 a of the holding capacitor, can thereby beformed simultaneously with the gate insulating film of the FET formingthe peripheral circuits, not with the gate insulating film of the pixelswitching FET. Thus, the thickness of the insulating film of the holdingcapacitor can be reduced to one third to one fifth of that of the aboveembodiment, and as a result, the capacitance can be increased by threeto five times.

[0078]FIG. 1(b) shows a cross-sectional view (FIG. 3 II-II) of aperiphery of a pixel region of an embodiment of the present invention.This is a structure for connecting the doping region 8, extending alongthe scanning direction (pixel row direction) of the pixel region, to thepredetermined voltage (V_(ss)). Reference numeral 80 indicates a P-typecontact region formed by the same step as that of the source/drainregions of the MOSFET of the peripheral circuits, such that afterforming the gate electrode, impurities having the same polarity areion-implanted with respect to the doping region 8 prepared beforeforming the gate electrode. The contact region 80 is connected to theline 70 via a contact hole 71, and the constant voltage V_(ss) isapplied thereto. The contact region 80 is also light-shielded by alight-shielding layer 14′, which is formed thereabove and which isformed of a third metallic layer. In other words, the light-shieldinglayer 14′ is formed in the peripheral region surrounding the entirepixel region and the light-shielding layer 14′ is separated from thepixel electrodes 14 of the pixels that are outermost in the pixelregion. The light-shielding layer 14′ is the same layer as the pixelelectrodes 14. A first metallic layer 12′ extends from thelight-shielding layer 12 that is outermost in the pixel region so as tolight-shield the light incident on the space between the outermost pixelelectrode 14 and the light-shielding layer 14′ in the peripheral region.

[0079]FIG. 2 is a cross-sectional diagram of an embodiment of a CMOScircuit element forming the peripheral circuits such as a drivingcircuit in the outside of the pixel region. In FIG. 2, the referencenumerals identify a substantially identical metallic layer, insulatingfilm, and semiconductor region formed by the identical steps as those ofFIG. 1.

[0080] In FIG. 2, numerals 4 a and 4 a′ indicate gate electrodes of anN-channel MOSFET and a P-channel MOSFET, respectively, forming theperipheral circuits (CMOS circuits), reference numerals 5 a (5 b) and 5a′ (5 b′) indicate an N-type doping region and a P-type doping region,respectively, each used to be the source (drain) region of the above,and 5 c and 5 c′ indicate channel regions. The contact region 80supplying a constant voltage to the P-type doping region 8 forming oneelectrode of the holding capacitor of FIG. 1 is formed by the same stepas that of the P-type doping region 5 a′ (5 b′) to be used as the source(drain) region of the P-channel MOSFET. Reference numerals 27 a and 27 cindicate source electrodes which are formed of a first metallic layerand connected to a power source voltage (0 V, 5 V, or 15 V), andreference numeral 27 b indicates a drain electrode formed of the firstmetallic layer. Reference numeral 32 a is a wiring layer formed of asecond metallic layer and is used as a line which connects elementsforming the peripheral circuits therebetween. Reference numeral 32 b isa power source line layer formed of the second metallic layer and isalso serves as a light-shielding layer. The light-shielding layer 32 bmay be connected to any constant voltage such as V_(c), LC-COM, or powersource voltage of 0 V, or it may be connected to inconstant voltagewhile being electrically separated from the power source line and thelike. Reference numeral 14′ is a third metallic layer, and in theperipheral circuit portion, the third metallic layer is used as alight-shielding layer to prevent light from being transmitted through asemiconductor region forming the peripheral circuits and from generatingcarriers which cause unstable voltage in the semiconductor region. Inother words, also in the peripheral circuits, light is light-shielded bythe second and third metallic layers.

[0081] As is mentioned above, the passivation film 17 in the peripheralcircuit portion may be a silicon nitride film, which is superior as aprotective film to the silicon oxide film forming the passivation filmof the pixel region, or may be a protective film having a double-layerstructure in which a silicon nitride film is formed on a silicon oxidefilm. Furthermore, although not particularly limited, the source/drainregions of the MOSFET forming the peripheral circuits of this embodimentmay be formed by a self-aligning manner. Any of the source/drain regionsof the MOSFET may have a LDD (lightly doped drain) structure or a DDD(double doped drain) structure. Off-set structure (in which the gateelectrode and the source/drain regions are positioned with a distancetherebetween) is preferably employed for the pixel switching FETconsidering the fact that the FET is driven by a large voltage and itmust prevent the light leakage current.

[0082] FIGS. 4(a), 4(b), and 4(c) each indicate another embodiment of aliquid crystal panel reflective-electrode-side substrate incorporated inthe present invention. In FIGS. 4(a) to 4(c), the reference numeralsidentify substantially identical layers and semiconductor regions formedby the identical steps as those of FIGS. 1 and 2.

[0083] In the embodiment shown in FIG. 4(a), an anti-reflection film 18formed of a material such as titanium nitride, i.e., TiN, is provided onthe back surface of the pixel electrodes 14 of the embodiment shown inFIG. 1. Such an anti-reflection film 18 further increases thelight-shielding effect as compared with that in the first embodiment ofFIG. 1. In other words, since the light-shielding layer 12 provided inthe first embodiment is formed of a metallic layer having a relativelyhigh reflectance, such as aluminum, the light obliquely incident on aspace between the pixel electrodes 14, as is shown by reference numeralA in FIG. 4(a), is reflected by the surface of the light-shielding layer12, is further reflected by the back surface of a pixel electrode 14,and then, by repeating such reflection. The light may finally leakthrough the opening 12 a, which is provided at the position of theconnecting plug 15, to the MOSFET side, reach the substrate, and resultin a light leakage current. However, when the anti-reflection film 18 isprovided, it can absorb the light incident on the space between thepixel electrodes 14, and thus the light leakage current can further beeffectively prevented. The preferred thickness of the anti-reflectionfilm 18 formed of titanium nitride (TiN) is 500 to 1000 angstroms. Theanti-reflection film 18 may not only be formed on the back surface ofthe pixel electrodes, but also on the surface of the light-shieldinglayer 12 or intermediately in the interlayer insulating layer.

[0084] The embodiment shown in FIG. 4(b) is constructed as follows: inthe embodiment shown in FIG. 4(a) in which the anti-reflection film 18is provided on the back surface of the pixel electrodes 14, a V-shapegroove 19 at least having a slope is formed between the adjacent pixelelectrodes on the surface of the third interlayer insulating film 13exposed to the space between the pixel electrodes 14. The lightvertically incident on the space between the pixel electrodes 14, as isshown by reference numeral B, is thereby reflected obliquely, and isabsorbed into the anti-reflection film 18 formed on the back surface ofthe pixel electrodes. Thus, the light, reflected by the surface of theinsulating film exposed to the space between the pixel electrodes or bythe underlying light-shielding layer, can be prevented from emergingwhile changing the direction by 180°. When such reflected light emerges,the image quality may deteriorate in a liquid crystal panel of anormally white mode in which the liquid crystal panel is allowed todisplay white by reflecting incident light when no voltage is applied tothe pixel electrodes, because the light emerging after being reflectedby the space between the pixel electrodes is displayed similarly to thelight reflected by a pixel electrode without an applied voltage.However, such reflected light can be eliminated by forming the V-shapegroove 19 as is shown in FIG. 4(b), in the interlayer insulating film13, thereby improving the image quality.

[0085] The embodiment shown in FIG. 4(c) is constructed as follows: inthe embodiment shown in FIG. 4(a) in which the anti-reflection film 18is provided on the back surface of the pixel electrodes 14, a V-shapedgroove 19 is formed along the border between the pixel electrodes on thesurface of the light-shielding layer 12 positioned below the spacebetween the pixel electrodes 14. Similar effects to those of theembodiment of FIG. 4(b) are thereby obtained.

[0086] Although the groove 19 in FIGS. 4(b) and 4(c) has a V-shapedcross-section, the cross-sectional shape of the groove 19 is not limitedto the V-shape, and as long as the inner face of the groove has a slope,the incident light is reflected by the slope and changes its directionshifted by 180° with respect to the incident direction so that thereflected light is absorbed into the anti-reflection film. The shape ofthe groove may be such that a slope is formed along the end portion ofone pixel electrode and a vertical face is provided along the endportion of the adjacent pixel electrode, or may be formed into asubstantial V-shape groove with a small flat portion at the bottom orinto a plurality of rows of such grooves.

[0087] In the above structures shown in FIGS. 4(a), 4(b) and 4(c), inaddition to the interlayer insulating film 13 formed of theabove-mentioned TEOS film (including the SOG film left by partialetching), a silicon nitride film may be formed thereunder between thereflective electrodes 14 and the underlying metallic layer as thelight-shielding layer 12. On the contrary, a silicon nitride film may beformed above the TEOS film 13. By employing such a double-layerstructure, to which the silicon nitride film is added, for theinterlayer insulating film 13, water or the like cannot readily enterthe resulting film, thereby improving moisture resistance. Theinterlayer insulating film having such a double-layer structure may beformed not only on the pixel region, but also on the second metalliclayers 32 a and 32 b in the peripheral region, and the moistureresistance is thereby improved in the peripheral region. In addition,since the refractive index of the silicon nitride film is between 1.9 to2.2, which value is higher than that of the silicon oxide film, i.e.,1.4 to 1.6, used for the protective insulating film 17, the incidentlight is reflected by the interface between the protective insulatingfilm 17 and the silicon nitride film, due to the difference in therefractive index when light is incident on the protective insulatingfilm 17 from the liquid crystal side. The amount of the light incidenton the interlayer film is thereby reduced. Thus, it is possible toprevent the phenomenon that carriers are generated by the light passingthrough the semiconductor region and destabilize the voltage in thesemiconductor region.

[0088]FIG. 5 is a plan layout showing a whole liquid crystal panelsubstrate (reflective-electrode-side substrate) incorporated in theabove embodiment.

[0089] In this embodiment, a light-shielding layer 25 is provided so asto prevent light from being incident on the peripheral circuits whichare provided in the periphery of the substrate, as is shown in FIG. 5.The light-shielding layer is formed from the same layer as that of thepixel electrodes 14. The peripheral circuits are provided around thepixel region 20 in which the pixel electrodes are arranged according toa matrix pattern. The peripheral circuits include: a data line drivingcircuit 21 supplying image signals, corresponding to image data, to thedata lines 7; a gate line driving circuit 22 scanning the gate lines 4in order; an input circuit 23 receiving image data input from outsidevia a pad region 26; a timing control circuit 24 controlling suchcircuits; and the like. These circuits are formed of MOSFETs, as activeelements or switching elements, formed by the same or different step forforming the pixel electrode switching MOSFET; and load elements such asresistors or capacitors.

[0090] In this embodiment, the light-shielding layer 25 is formed of athird metallic layer formed by the same step as that of the pixelelectrodes 14 shown in FIG. 1, and a predetermined voltage such as thepower source voltage, the center voltage of the image signals, or the LCcommon voltage is applied to the light-shielding layer 25. By applyingthe predetermined voltage to the light-shielding layer 25, thereflection can be reduced as compared with applying a floating or othervoltage. The light-shielding layer 25 can be allowed to float withoutconnecting to a power source line. Displaying errors can thereby beavoided in the peripheral region, since the light-shielding layer 25does not apply a voltage to the liquid crystal layer.

[0091] Reference numeral 26 indicates the pad region in which a pad orterminal used for supplying the power source voltage is formed. Thesealing member 36 is arranged such that the pad region 26 to whichsignals are input from outside is positioned outside the sealing member36.

[0092]FIG. 6 shows the cross-sectional structure of a reflective-typeliquid crystal panel to which the liquid crystal panel substrate 31 isapplied. As is shown in FIG. 6, a support substrate 32 made of glass,ceramic, etc. is adhered to the back surface of the liquid crystal panelsubstrate 31 using an adhesive. Furthermore, an incident-side glasssubstrate 35, which is provided with an opposing electrode (also calledas common electrode) 33 made of a transparent conductive film (ITO), andto which the LC common voltage is applied, is positioned at the surfaceside of the liquid crystal panel substrate 31 with an appropriatedistance therebetween, and a known TN (Twisted Nematic) type liquidcrystal or a SH (Super Homeotropic) type liquid crystal 37, in whichliquid crystal molecules are aligned substantially homeotropicallywithout an applied voltage, is poured into the resulting space sealed bythe sealing member 36 to complete the liquid crystal panel 30.

[0093] The light-shielding layer 25 on the peripheral circuits isarranged to face the opposing electrode 33 with the liquid crystal 37interposed therebetween. Since the LC common voltage is applied to theopposing electrode 33, by applying the LC common voltage to thelight-shielding layer 25, no do voltage is applied to the liquid crystalinterposed therebetween. Therefore, the liquid crystal molecules arealways twisted by approximately 90° in the case of the TN-type liquidcrystal, and are always aligned homeotropically in the case of theSH-type liquid crystal.

[0094] In this embodiment, the strength of the liquid crystal panelsubstrate 31 formed of a semiconductor substrate is significantlyincreased because the liquid crystal panel substrate 31 has the supportsubstrate 32 made of glass, ceramic, etc. adhered to the back surfacethereof using the adhesive. As a result, by joining the opposingsubstrate to the liquid crystal panel substrate 31 after adhering thesupport substrate 32 to the liquid crystal panel substrate 31, a uniformgap is advantageously obtained in the liquid crystal layer of the entirepanel.

[0095] (Explanation of Liquid Crystal Panel Substrate Using InsulatingSubstrate)

[0096] Although the structure of a liquid crystal panel substrate usinga semiconductor substrate and a liquid crystal panel employing theliquid crystal panel substrate is explained above, the structure of areflective-type liquid crystal panel substrate using an insulatingsubstrate such as glass will be described below.

[0097]FIG. 10 shows a cross-sectional view of the structure of a pixelin a reflective-type liquid crystal panel substrate. Similarly to FIG.1, this figure shows a cross-sectional view taken along line I-I of theplan layout shown in FIG. 3. In this embodiment, a TFT is employed as atransistor for switching the pixel. In FIG. 10, the reference numeralsidentify layers and semiconductor regions having substantially identicalfunctions as those of FIGS. 1 and 2. Reference numeral 1 indicates asilica or non-alkaline glass substrate having a single-crystal,polycrystalline, or amorphous silicon film (the layer forming 5 a, 5 b,5 c, and 8) formed thereon, and insulating films 4 b and 9 b, having adouble-layer structure formed of a silicon oxide film formed by heatoxidation and another silicon oxide film or silicon nitride filmdeposited by CVD, are formed on the silicon film. Before forming theupper silicon oxide film or silicon nitride film of the insulating film4 b, N-type impurities are doped into the regions 5 a, 5 b, and 8 of thesilicon film to form the source region 5 a and drain region 5 b of aTFT, and the electrode region 8 of the holding capacitor. Furthermore, awiring layer which is made of poly-silicon, metallic silicide, etc., andwhich is to be used as the gate electrode 4 a of the TFT and the otherelectrode 9 a of the holding capacitor, is formed on the insulating film4 b. As is mentioned above, the TFT formed of the gate electrode 4 a,the gate insulating film 4 b, the channel 5 c, the source 5 a, and thedrain 5 b, and the holding capacitor formed of the electrodes 8 and 9 aand the insulating film 9 b are formed.

[0098] In addition, the first interlayer insulating film 6 made ofsilicon nitride or silicon oxide is formed on the wiring layers 4 a and9 a, and the source electrode 7 a connected to the source region 5 a viaa contact hole made in the insulating film 6, is formed by a firstmetallic layer formed of an aluminum layer. The interlayer insulatingfilm 11 and the light-shielding layer 12 are formed on the firstmetallic layer similarly to those shown in FIG. 1. The second interlayerinsulating film 13 formed of silicon oxide, silicon nitride, or adouble-layer of silicon oxide and silicon nitride is formed on thelight-shielding layer 12. The second interlayer insulating film 13 isplanarized by the CMP method, and pixel electrodes, to be used asreflective electrodes, are formed from aluminum for each pixel on theplanarized second interlayer insulating film 13. The electrode region 8of the silicon film and the pixel electrode 14 are electricallyconnected via the contact hole 16. Similarly to that shown in FIG. 1,this connection is achieved by embedding the connecting plug 15 made ofa refractory metal such as tungsten. The light-shielding layer 12 isformed on the portion corresponding to the cross-sectional diagram ofFIG. 1(b), and a light-shielding layer 12′, which light-shields thelight incident on a space between the pixel electrode 14 and thelight-shielding layer 14′ light-shielding the peripheral region of thepixel electrode 14, is formed as a second metallic layer below the pixelelectrode 14 and the light-shielding layer 14′.

[0099] As is mentioned above, since the reflective electrode ispositioned above the TFT and holding capacitor formed on the insulatingsubstrate, the pixel electrode region increases, and the holdingcapacitor also can be formed in a larger area under the reflectiveelectrode similarly to the plan layout of FIG. 3. Thus, even in a highresolution (small pixel) panel, the drive is stabilized because thevoltage applied to each pixel can be maintained, and in addition, a highaperture ratio (reflectance) can be achieved.

[0100] As is similar to the above embodiments, the passivation film 17formed of a silicon oxide film is formed on the reflective electrode 14.The structure of the liquid crystal panel substrate as a whole and thatof the liquid crystal panel are similar to those shown in FIGS. 5 and 6.Therefore, the peripheral circuits such as the driving circuit employthe TFT as a transistor element. In the peripheral region including theperipheral circuit portion, the second metallic layers 32 a and 32 b areformed above the CMOS type TFT as connecting lines between the elementsand as a light-shielding layer elongated or separated therefrom, as issimilar to FIG. 2.

[0101] If light also enters from below the substrate, anotherlight-shielding layer may be provided under the silicon films 5 a, 5 b,and 8. Although the top-gate type in which the gate electrode ispositioned above the channel is shown in the figure, it is also good toprovide the bottom-gate type in which the gate electrode is formedbeforehand, and a silicon film to be used as the channel on a gateinsulating film interposed therebetween may be employed. Furthermore,moisture resistance of the peripheral circuit region can be improved byemploying the silicon nitride film or the double-layer structure filmformed of a silicon oxide film and a silicon nitride film.

[0102] (Explanation of Electronic Equipment Using the Reflective-TypeLiquid Crystal Panel of the Present Invention)

[0103]FIG. 8 shows electronic equipment using a liquid crystal panel ofthe present invention, and is a plan diagram illustrating the mainportion of a projector (projection type display device) usingreflective-type liquid crystal panels of the present invention as lightvalves. FIG. 8 shows a polarizing illuminator 100 having a light sourceportion 110 positioned on the center line of an optical element 130, anintegrator lens 120, and the polarization conversion element 130; apolarization beam splitter 200 reflecting the S-polarized light beam,emerging from the polarizing illuminator 100, by a S-polarized lightreflection surface 201; a dichroic mirror 412 separating a blue light(B) component from the light reflected by the S-polarized lightreflection surface 201 of the polarization beam splitter 200; areflective-type liquid crystal light valve 300B modulating the separatedblue light (B); a dichroic mirror 413 reflecting the light, from whichthe blue light has been separated, and separating a red light (R)component therefrom; a reflective-type liquid crystal light valve 300Rmodulating the separated red light (R); a reflective-type liquid crystallight valve 300G modulating the residual green light (G) transmittedthrough the dichroic mirror 413; and a projection optical system 500formed of projection lenses by which light, that is modulated by thethree reflective-type liquid crystal light valves 300R, 300G, and 300Band then synthesized by the dichroic mirrors 412 and 413 and thepolarization beam splitter 200, is projected on a screen 600. Each ofthe three reflective-type liquid crystal light valves 300R, 300G, and300B is provided with the liquid crystal panel.

[0104] The randomly polarized light beam emerging from the light sourceportion 110 is separated into a plurality of intermediate light beams bythe integrator lens 120, converted into one type of polarized lightbeams (S-polarized light beams) polarized in substantially the samedirection by the polarization conversion element 130 having a secondintegrator lens on the light-incident side, and reaches the polarizationbeam splitter 200. The S-polarized light beams emerging from thepolarization conversion element 130 are reflected by the S-polarizedlight reflection surface 201 of the polarization beam splitter 200, andamong the reflected light beams, the blue light (B) beams are reflectedby the blue light reflection layer of the dichroic mirror 412 and aremodulated by the reflective-type liquid crystal light valve 300B. Amongthe light beams transmitted through the blue light reflection layer ofthe dichroic mirror 412, the red light (R) beams are reflected by thered light reflection layer of the dichroic mirror 413 and are modulatedby the reflective-type liquid crystal light valve 300R.

[0105] Meanwhile, the green light (G) beams transmitted through the redlight reflection layer of the dichroic mirror 413 are modulated by thereflective-type liquid crystal light valve 300G. The reflective-typeliquid crystal panel in which modulation is carried out by thereflective-type liquid crystal light valves 300R, 300G, and 300Baccording to the above-mentioned manner employs the TN-type liquidcrystal (in which the major axis of liquid crystal molecules is alignedsubstantially parallel to the panel substrate under no applied voltage)or the SH-type liquid crystal (in which the major axis of liquid crystalmolecules is aligned substantially perpendicular to the panel substrateunder no applied voltage).

[0106] When employing the TN-type liquid crystal, in a pixel (OFF pixel)in which a voltage below the threshold voltage of the liquid crystal isapplied to the liquid crystal layer interposed between the reflectiveelectrode of the pixel and the common electrode of the opposingsubstrate, the incident color light is elliptically polarized by theliquid crystal layer, is reflected by the reflective electrode, andemerges via the liquid crystal layer as the nearly ellipticallypolarized light beams whose polarization axis component is almostentirely shifted by substantially 90° from the polarization axis of theincident color light. Meanwhile, in a pixel (ON pixel) in which avoltage is applied to the liquid crystal layer, the incident color lightreaches the reflective electrode unchanged, is reflected, and emergeswhile maintaining the same polarization axis as that of the incidentlight. Since the alignment angle of the liquid crystal molecules of theTN-type liquid crystal changes according to the voltage applied to thereflective electrode, the angle of the polarization axis of thereflected light with respect to the incident light varies with thevoltage applied to the reflective electrode via the transistor of thepixel.

[0107] In addition, when employing the SH-type liquid crystal, in apixel (OFF pixel) in which the voltage applied to the liquid crystallayer is below the threshold voltage of the liquid crystal, the incidentcolor light reaches the reflective electrode unchanged, is reflected,and emerges while maintaining the same polarization axis as that of theincident light. Meanwhile, in a pixel (ON pixel) in which a voltage isapplied to the liquid crystal layer, the incident color light iselliptically polarized by the liquid crystal layer, is reflected by thereflective electrode, and emerges via the liquid crystal layer as thenearly elliptically polarized light beams whose polarization axiscomponent is almost entirely shifted by substantially 90° from thepolarization axis of the incident light. Similarly to the TN-type liquidcrystal, the alignment angle of the liquid crystal molecules of theSH-type liquid crystal changes according to the voltage applied to thereflective electrode, and the angle of the polarization axis of thereflected light with respect to the incident light varies with thevoltage applied to the reflective electrode via the transistor of thepixel.

[0108] Among the color light reflected by the pixels of the liquidcrystal panel, the polarization beam splitter 200, which reflectsS-polarized light, passes the P-polarized component, but does not passthe S-polarized component. The light transmitted through thepolarization beam splitter 200 forms an image. Therefore, when theTN-type liquid crystal is employed for the liquid crystal panel, theprojected image is in the normally white mode, since the reflected lightof the OFF pixel reaches the projection optical system 500 and that ofthe ON pixel does not reach the lens. When the SH-type liquid crystal isemployed, the projected image is in the normally black mode, since thereflected light of the OFF pixel does not reach the projection opticalsystem and that of the ON pixel reaches the projection optical system500.

[0109] According to the reflective-type liquid crystal panel, byutilizing a semiconductor technique, a larger number of pixels can beformed and the panel size can be reduced as compared with active-matrixliquid crystal panel having a TFT array formed on a glass substrate.Thus, images with higher resolution can be projected by smaller-sizedprojectors.

[0110] As is described with reference to FIG. 6, the peripheral circuitportion of the liquid crystal panel is covered with a light-shieldinglayer and the same voltage (e.g., LC common voltage, however, if the LCcommon voltage is not applied, a voltage different from the opposingelectrode of the pixel portion is applied, thus a peripheral opposingelectrode is separated from the opposing electrode of the pixel portion)as that applied to the opposing electrode formed on the opposingsubstrate is applied to the peripheral circuit portion. Thus,substantially 0 V is applied to the liquid crystal interposedtherebetween and the liquid crystal is in the OFF state. Therefore, inaccordance with the normally white mode, the entire periphery of theimage region can display white mode in a TN-type liquid crystal panel,and the entire periphery of the image region can display black mode in aSH-type liquid crystal panel in accordance with the normally black mode.

[0111] According to the above embodiment, the voltage applied to each ofthe reflective-type liquid crystal panels 300R, 300G, and 300B issufficiently maintained and also the reflectance of each pixel electrodeis extremely high. Thus, sharp images can be obtained.

[0112] FIGS. 9(a), 9(b) and 9(c) show an outside view of electronicequipment employing a reflective-type liquid crystal panel of thepresent invention. The reflective-type liquid crystal panels employed inthese electronic equipment fundamentally have the same structure asthose used as the light valves, except that the reflective electrodesare not required to have a completely reflective face, and far from it,the reflective electrodes preferably have an appropriately roughenedsurface to increase the angle of view because the reflective-type liquidcrystal panels are used as direct viewing reflective-type liquid crystalpanels in these electronic equipment and are not used as light valvescombined with a polarization beam splitter.

[0113]FIG. 9(a) is a perspective view showing a cellular telephone.Reference numeral 1000 indicates the main body of the cellular telephoneand reference numeral 1001 indicates a liquid crystal display portionusing a reflective-type liquid crystal panel of the present invention.

[0114]FIG. 9(b) shows wrist-watch-type electronic equipment. Referencenumeral 1100 indicates the main body of the watch. Reference numeral1101 indicates a liquid crystal display portion using a reflective-typeliquid crystal panel of the present invention. Since the liquid crystalpanel has pixels of higher resolution as compared with conventionalwatch display portion, it can display TV images, achievingwristwatch-type TVs.

[0115]FIG. 9(c) shows a mobile data-processing device of a wordprocessor or a personal computer. Reference numeral 1200 indicates thedata-processing device, reference numeral 1202 indicates an input unitsuch as a keyboard or the like, reference numeral 1206 indicates adisplay portion using a reflective-type liquid crystal panel of thepresent invention, and reference numeral 1204 indicates the main body ofthe data-processing device. Since each of the electronic equipment isdriven by batteries, the life-time of the batteries can be extended byusing a reflective-type liquid crystal panel that does not have a lightsource lamp. In addition, as is mentioned in the present invention, theperipheral circuits can be built in the panel substrate; the number ofcomponents is largely reduced, and more light-weight and smaller-sizedequipment can be achieved.

[0116] In the above embodiments, the TN-type liquid crystal, and theSH-type liquid crystal which is homeotropically aligned, are employed asthe liquid crystal for liquid crystal panels. However, the presentinvention can be realized by using other types of liquid crystals.

[0117] As is mentioned above, according to the present invention, alight-shielding layer is made between a pixel electrode, which is usedas a reflective electrode, and a conductive layer, which constitutes aterminal electrode of a switching element applying a voltage to thepixel electrode, such that in the pixel region, the light-shieldinglayer has only an opening for forming a contact hole connecting thepixel electrode and the terminal electrode. Thus, the amount of lightleaking from the incident side to the driving-element side can bereduced to substantially zero and the amount of a light leakage currentflowing in a semiconductor layer or semiconductor substrate can belargely decreased.

[0118] In addition, in a reflective-type liquid crystal panel having apixel region, in which the pixel electrodes are arranged in a matrixpattern, and peripheral circuits provided around the pixel region on thesame substrate, a light-shielding layer formed of the same layer as ametallic layer forming the reflective electrodes in the pixel region isprovided for the peripheral circuits. Thus, without increasing thenumber of process steps, the amount of light leakage in the pixel regionand the peripheral circuits can be reduced, thereby decreasing the lightleakage current.

[0119] Moreover, in a reflective-type liquid crystal panel having apixel region, in which the pixel electrodes are arranged in a matrixpattern, and peripheral circuits provided around the pixel region on thesame substrate, a light-shielding layer of the pixel region is formedbelow the pixel electrode layer from a layer used as a wiring layer or alight-shielding layer of the peripheral circuits. Thus, thelight-shielding layer can be formed without increasing the number ofprocess steps.

[0120] Furthermore, since an anti-reflection film is formed at thebottom side of the pixel electrode, the light reflected by the surfaceof the light-shielding layer can be absorbed, even if thelight-shielding layer is formed of a metallic layer having a relativelyhigh reflectance. Thus, the following phenomenon can be prevented: thelight repeatedly reflected between the surface of the light-shieldinglayer and the back surface of the pixel electrode leaks through anopening provided at the portion of a conductor which connects a pixelelectrode and a switching electrode, reaches the semiconductor layer orthe semiconductor substrate, and generates a light leakage current.

[0121] In addition, an anti-reflection film is formed at the bottom sideof the pixel electrode and a groove at least having a slope is formedbetween pixel electrodes on the surface of an insulating film exposed toa space between the pixel electrodes in the pixel region or on thesurface of a light-shielding layer below the insulating film. Thus, thelight incident on the space between the pixel electrodes is reflected inan oblique direction and is absorbed into the anti-reflection film onthe back surface of the pixel electrodes so that the light reflected bythe surface of the insulating film, exposed to the space between thepixel electrodes, or the light-shielding layer below the insulatingfilm, is prevented from emerging while changing its direction by 180°.Therefore, the image quality can be improved.

What is claimed is:
 1. A substrate having a pixel electrode, comprising:a substrate; a plurality of pixel units, each pixel unit including apixel electrode useable as a reflective electrode and a switchingelement electrically connected to said pixel electrode, said pixel unitsbeing arranged in a matrix pattern on the substrate, the switchingelement having a terminal electrode forming a conductive layer,connecting wiring provided between the pixel electrode and theconductive layer that electrically connects said pixel electrode andsaid terminal electrode; a light-shielding layer having an openingsurrounding a portion in which said connecting wiring is formed andhaving no opening in regions between adjacent pixel electrodes, saidlight-shielding layer being formed between said pixel electrode and saidconductive layer; and an underlying insulating layer being formed belowthe pixel electrodes, and in regions between adjacent pixel electrodesof the plurality of pixel units, a groove having substantial V-shapedsurface relative to an upper surface of the underlying insulating layerbeing formed in regions between pixel electrodes on a surface of theunderlying insulating layer or on a surface of said light-shieldinglayer under said underlying insulating layer for reflecting obliquelythe light vertically incident which enters a space between the pixelelectrodes.
 2. The substrate having a pixel electrode as set forth inclaim 1, wherein an antireflection film is provide between said pixelelectrode and said light-shielding layer.
 3. The substrate having apixel electrode as set forth in claim 2, wherein said antireflectionfilm has substantially the same shape as that of said pixel electrodeand is provided below said pixel electrode.
 4. The substrate having apixel electrode as set forth in claim 2, wherein said antireflectionfilm comprises titanium nitride.
 5. The substrate having a pixelelectrode as set forth in claim 4, wherein the film thickness of saidtitanium nitride is 500 to 1000 angstroms.
 6. The substrate having apixel electrode as set forth in claim 1, said antireflection film havingsubstantially the same shape as that of said pixel electrode, and beingprovided below said pixel electrode.
 7. The substrate having a pixelelectrode as set forth in claim 6, wherein said antireflection filmcomprises titanium nitride.
 8. The substrate having a pixel electrode asset forth in claim 7, wherein the film thickness of said titaniumnitride is 500 to 1000 angstroms.
 9. The substrate having a pixelelectrode as set forth in claim 1, wherein said contact hold is providedat a substantially central position of the plane of said pixelelectrode.
 10. A substrate having a pixel electrode, comprising: asubstrate; a plurality of pixel units, each pixel unit including a pixelelectrode useable as a reflective electrode and a switching elementelectrically connected to said pixel electrode, said pixel units beingarranged in a matrix pattern on the substrate, the switching elementhaving a terminal electrode forming a conductive layer, connectingwiring provided between the pixel electrode and the conductive layerthat electrically connects said pixel electrode and said terminalelectrode; a light-shielding layer having an opening surrounding aportion in which said connecting wiring is formed and having no openingin regions between adjacent pixel electrodes, said light-shielding layerbeing formed between said pixel electrode and said conductive layer; andan underlying insulating layer being formed below the pixel electrodes,and in regions between adjacent pixel electrodes of the plurality ofpixel units, a groove defined by a pair of sloping surfaces relative toan upper surface of the underlying insulating layer being formed inregions between pixel electrodes on a surface of the underlyinginsulating layer or on a surface of said light-shielding layer undersaid underlying insulating layer, the pair of sloping surfaces of thegroove being opposed to each other for reflecting obliquely the lightvertically incident which enters a space between the pixel electrodes.11. A substrate having a pixel electrode, comprising: a substrate; aplurality of pixel units, each pixel unit including a pixel electrodeuseable as a reflective electrode and a switching element electricallyconnected to said pixel electrode, said pixel units being arranged in amatrix pattern on the substrate, the switching element having a terminalelectrode forming a conductive layer, connecting wiring provided betweenthe pixel electrode and the conductive layer that electrically connectssaid pixel electrode and said terminal electrode; a light-shieldinglayer having an opening surrounding a portion in which said connectingwiring is formed and having no opening in regions between adjacent pixelelectrodes, said light-shielding layer being formed between said pixelelectrode and said conductive layer; and an underlying insulating layerbeing formed below the pixel electrodes, and in regions between adjacentpixel electrodes of the plurality of pixel units, a groove defined by apair of sloping surfaces relative to an upper surface of the underlyinginsulating layer being formed in regions between pixel electrodes on asurface of the underlying insulating layer or on a surface of saidlight-shielding layer under said underlying insulating layer, the groovehaving no flat surface on bottom for reflecting obliquely the lightvertically incident which enters a space between the pixel electrodes.